Frets for stringed musical instruments, particularly guitars, banjos and the like, provide a mechanism for stopping vibrations of the strings at spaced locations on the playing surface (fingerboard or fretboard) of the neck of the instrument over which the strings extend in tension to produce the desired musical tones when the strings are actuated, such as by plucking, strumming or picking. Frets are positioned transversely along the longitudinal dimension of the neck (and generally perpendicularly to the strings) beneath the strings at predetermined spaced locations, and thus string length can be effectively adjusted by pressing the strings into contact with a particular fret. This presets the length of the vibrating portion of the string, thereby controlling the frequency of the tone produced. The fingerboard may be integral with the neck and made of the same material as the neck, or it may be made of a different material and coupled to the neck such as by lamination. It may be flat or slightly radiused.
Conventional frets are made of metal and are generally T-shaped. The stem or tang of the fret is embedded into or otherwise secured to the instrument neck, and the crown or head of the fret extends above the surface of the neck and provides the working surface against which the string or strings are finger-pressed to create the desired tone. The tang may have one or more barbs to help anchor or secure the fret in the fingerboard.
The first guitar frets were “bar” frets made from flat stock. These frets project square out of the neck and had no mushroom crown. They measured about 0.50″×0.200″×X″ long. Some manufacturers actually had 4 or 5 gauges of bar fret stock ranging from about 0.045″ to 0.058″. The limited quality control at that time meant that there were also thickness deviations within each gauge.
These bar frets were hammered into the sawn fret slots in the fingerboard to a depth of about 0.100″ and became integral to the neck. The various gauges were employed to control the shape of the neck from the side view. They were used to counter the string tension that would otherwise cause the neck to bow. Given the tapered shape of the neck, and the different string gauges from bass to treble, neck bow would be irregular.
The bar frets were used to hold the line of the neck when under string tension. When the luthier was satisfied with the bar fret choice and placement, the tops of the bars were filed down to somewhat uniform height to ease playability. The bar frets transferred the string vibration directly to the neck. In this way, the frets became part of the structure of the neck. It is a simple structure as one side/back is in tension and the other side/front is in compression. As such, the neck resonated in response to playing. The integral bar frets transferred the string vibration directly into the neck and contributed to the overall tonal quality of the instrument. It is almost universally agreed on by players and listeners that such early guitars, with bar frets, have incomparable tonal qualities.
Necks with such bar frets do not require a truss rod (though an embedded stiffener of stronger wood or metal, including a truss rod, can be used).
The use of bar frets was discontinued in the mid 1930's—except for use in restoration and a few guitars built by certain luthiers. Their correct use was an art. They were difficult to use, install, and get “right”. There was no significant reinforcement in those necks so the fit of the frets had to be precise. These old style bar frets were square on top, and had to be left high enough to accommodate for hills and valleys in the actual neck line. After installation they were typically filed by hand into adequate playability.
Modern frets have a typical tang that is 0.020″ thick and is perforated to make little barbs that secure the fret in the neck like weather stripping. Since the tang is so thin and flimsy, the modern fret wire does not play a role in supporting the neck by becoming integral to the neck. Necks using such fret wire require a truss rod to counter string tension and hold the neck straight. Steel T-Bars and square steel tube were used before the single action adjustable truss rod appeared. Currently, a single or double action truss rod to control the neck and modern frets glued in oversized slots are used. Modern frets have no structural role in the neck. They are simply held in an oversize slot by their barbed (springy) tang and glue. Wire fret/truss rod necks do not seem as tonally alive as bar fret necks.
In order for each string to have room to vibrate, clearance provided by the nut/bridge height relationship or a slight curvature must be formed in the neck. If the strings sit too high above the neck surface, the instrument is difficult to play. If the strings sit too low above the neck surface, they buzz against the frets.
Recently, the Plek® machine was developed to set up stringed instruments using computer numerical control (CNC) to level and shape fretboards and frets in an efficient manner. The instrument is scanned to measure the position of each string on the fretboard, typically at the first and twelfth frets. The measured results are compared to a suggested optimum, and the truss rod in the neck is adjusted to obtain the desired relief for the neck. The strings are then removed, and the frets are cut based upon the measurements made. The relief of the neck created by the string tension is taken into account while calculating the process parameters.
It would be desirable to obtain the stability and tonal performance advantages of bar frets while eliminating the concomitant set up difficulties of the prior art. It also would be desirable to provide neck technology that maximizes stability, playability, and tonal response in stringed instruments, particularly guitars.